The following paragraphs are not an admission that anything discussed in them is prior art or part of the knowledge of persons skilled in the art.
U.S. Pat. No. 3,958,628 describes a vertical blower coil unit for heating and cooling.
U.S. Pat. No. 5,497,823 describes an energy recovery ventilator (ERV) for exchanging indoor air with outdoor air.
U.S. Pat. No. 7,942,193 describes a defrost system for a heat recovery ventilator/energy recovery ventilator (HRV/ERV).